Controlling method of washing machine

ABSTRACT

A control method of a washing machine reliably guarantees a rinsing performance, and a minimized number of rinsing cycles is performed. The method includes: circulating detergent water collected in a tub through a circulation passage during a washing cycle; supplying a voltage to a pair of electrodes made of different materials and installed on the circulation passage to determine whether a quantity of detergent contained in the detergent water is excessive; circulating rinsing water collected in the tub through the circulation passage during a rinsing cycle; detecting a magnitude (I2) of a current flowing through the rinsing water by supplying the voltage to the pair of electrodes; and comparing the detected magnitude (I2) of the current with a reference value (Ir), and finishing the rinsing cycle when the detected magnitude (I2) is equal to or less than the reference value (Ir).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 2007-034407, filed on Apr. 6, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

The present invention relates to a control method of a washing machine, and more particularly to a control method of a washing machine in which a rinsing performance is reliably guaranteed and a rinsing cycle is performed as many times as is proper.

2. Description of the Related Art

If a user inputs a desired washing course, a washing machine washes laundry through processes of washing, rinsing, and dehydrating in accordance with a predetermined washing course. A designer determines and sets the number of times of rinsing generally utilized with the respective washing courses when designing a washing machine, and the rinsing of the laundry is performed by the set times of the rinsing.

However, if the laundry is always rinsed a predetermined number of times even though there are differences in quantity, kind, and solubility of detergent added by the user, the rinsing performance of the washing machine cannot be reliably guaranteed, and water and electricity are frequently overused.

To solve the above-mentioned problem, Korean Unexamined Patent Application Publication No. 2003-44491 discloses an automatic rinsing control method of a washing machine of measuring turbidity of rinsing water using a photo sensor, of additionally performing the rinsing cycle when the measured turbidity is greater than a predetermined degree, and of finishing the rinsing cycle when the measured turbidity of the rinsing water is less than the predetermined degree.

However, in the disclosed control method, when a foreign substance is put between a light emitting unit and a light receiving unit of the photo sensor, there is a high chance that a malfunction will occur such that the turbidity of the rinsing water appears to be greater than a predetermined degree, in spite of the turbidity being less than the predetermined degree, and the rinsing cycle is performed continuously.

Meanwhile, the user distrusts the rinsing performance of the washing machine and sets an excessive number of times of rinsing by extra times of the rinsing to the predetermined number of times. However, when the rinsing cycle added by the user is performed even though there is no necessity to perform the number of times of the rinsing set by the user in order to rinse the laundry efficiently, water and electric power are wasted, and it is a longer process to wash the laundry. Thus, the user is inconvenienced.

SUMMARY

The present invention has been made in view of the above-mentioned problems. An aspect of the invention provides a control method of a washing machine that guarantees a reliable rinsing performance of the washing machine and prevents undesired energy from being consumed.

In accordance with one aspect, an embodiment of the present invention provides a control method of a washing machine that measures a turbidity of the rinsing water and determines whether a rinsing cycle is finished, comprising: circulating the rinsing water through a circulation passage by driving a circulation device; measuring a magnitude of current flowing through the rinsing water by supplying a voltage to electrodes installed on the circulation passage; and comparing the detected magnitude (I2) with a reference value (Ir) and determining whether the rinsing cycle is finished based on the comparison result.

Generally, when the detected magnitude (I2) of the current is equal to or less than the reference value (Ir), the rinsing cycle is finished and when the detected magnitude (I2) of the current is greater than the reference value (Ir), another rinsing cycle is added and performed.

In an embodiment, control method of a washing machine further comprises: circulating detergent water through the circulation passage during a washing cycle performed prior to the rinsing cycle; detecting the magnitude of the current flowing in the detergent water by supplying a voltage to the electrodes; and determining whether a quantity of detergent added by a user is excessive by comparing the detected magnitude (I1) with a reference value (Iw).

In this embodiment, when the detected magnitude (I1) is equal to or greater than the reference value (Iw), information that the excess detergent is being utilized is displayed on a display. Moreover, when the detected magnitude (I1) is equal to or greater than the reference value (Iw), the number of rinsing cycle times is increased, and an elongated washing time is displayed on a display. Thus, when the detected magnitude (I1) is equal to or greater than the reference value (Iw), a quantity of the rinsing water to be supplied at an initial rinsing cycle is re-set.

The electrodes are made of different materials, and the control method further comprises changing polarities of the voltage to be supplied to the electrodes for a predetermined time before the rinsing cycle is finished.

Either of the electrodes comprises a silver electrode containing silver, and the other comprises a titanium electrode containing titanium. The titanium electrode is regarded as a positive electrode when the voltage is supplied to the electrodes.

Moreover, the control method further comprises: counting the number of rinsing cycle times; and finishing the rinsing cycle based on a result of comparing the counted number of times of a rinsing cycle with a maximum number of times of a rinsing cycle.

In accordance with another aspect, in an embodiment, the present invention provides a control method of a washing machine comprising: circulating detergent water collected in a tub through a circulation passage during a washing cycle; supplying a voltage to a pair of electrodes made of different materials and installed on the circulation passage to determine whether a quantity of detergent contained in the detergent water is excessive; circulating rinsing water collected in the tub through the circulation passage during a rinsing cycle; detecting a magnitude of current flowing through the rinsing water by supplying the voltage to the pair of electrodes; and comparing the detected magnitude (I2) of current with a reference value (Ir) and finishing the rinsing cycle when the detected magnitude (I2) is equal to or less than the reference value (Ir).

In such an embodiment, the control method further comprises: counting the number of rinsing cycle times; and finishing the rinsing cycle even when the detected magnitude (I2) exceeds the reference value (Ir) when the counted number of times of rinsing cycle reaches the maximum number of times of rinsing cycle.

Either of the pair of electrodes comprises a silver electrode containing silver, and the other comprises a titanium electrode containing titanium.

The titanium electrode is regarded as a positive electrode when the voltage is supplied to the pair of electrodes.

The voltage is supplied by regarding the silver electrode as a positive electrode for a predetermined time before the rinsing cycle is finished.

When it is determined that an excessive quantity of the detergent is contained in the detergent water, information that the excessive quantity of the detergent is contained is displayed on a display, and a quantity of the rinsing water to be supplied at an initial rinsing cycle is re-set.

Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view illustrating a washing machine employing a control method according to an embodiment of the present invention;

FIG. 2 is a schematic view partially illustrating the washing machine in FIG. 1;

FIG. 3 is a block diagram illustrating the control of the washing machine according to an embodiment of the present invention; and

FIGS. 4A and 4B are flowcharts illustrating the control method of a washing machine according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.

FIG. 1 is a perspective view illustrating a washing machine employing a control method according to an embodiment of the present invention, FIG. 2 is a schematic view partially illustrating the washing machine in FIG. 1, and FIG. 3 is a block diagram illustrating the control of the washing machine according to an embodiment of the present invention.

As illustrated in FIGS. 1 to 3, a washing machine to which a control method according to the present invention is applied includes a drum type tub 11 installed in a main body 10 to accommodate water (washing water or rinsing water), and a cylindrical rotation drum 12 installed in the tub 11 to rotate. Here, the terms ‘washing water’ and ‘rinsing water’ indicate waters to be supplied to the tub 11 during a washing cycle and a rinsing cycle.

A door 13 is installed in the front side of the main body 10 to open and close an opening through which laundry is put in or taken out, and a control panel (not shown) is installed to control operation of a drum type washing machine. The control panel (not shown) is typically provided with various buttons and a jog dial such that a user can control the operation of the washing machine, and with a display 14 (See FIG. 3) to display an operational status of the washing machine.

A detergent feeder 20 to feed detergent and a water supply 30 to supply water (washing water or rinsing water) are installed in the upper side of the tub 11, and an exhaust device, including an exhaust pipe 41 and an exhaust valve 42 that exhausts the water from the tub 11, are installed in the lower side of the tub 11. Moreover, a driving motor 15 (See FIG. 3, and not shown in FIGS. 1 and 2) to rotate the rotation drum 12 is installed in the rear outer side of the tub 11 to perform the washing operation, the rinsing operation, and the dehydrating operation.

The detergent feeder 20 has an inner space divided into a plurality of spaces and is installed in the front side of the main body 10 such that the user may easily add the detergent and rinse into the respective spaces. The divided spaces include a spare washing detergent container to accommodate the detergent, a main washing detergent container to accommodate the detergent used in main washing, and a rinse container to accommodate a rinse used in rinsing.

The water supply 30 is connected to an external water supplying hose, and includes a water supply valve 31 to control the supply of water, a connecting pipe 32 to connect the water supply valve 31 to the detergent feeder 20, and a water supply pipe 33 to guide water passing through the detergent feeder 20 into the tub 11. This configuration is intended to manage the water that is supplied to the tub 11 and passes through the detergent feeder 20 so that the detergent in the detergent feeder 20 can be fed into the tub 11 together with the water.

The washing machine employing the control method of the present invention includes a circulation device 50 to circulate the water in the tub 11. The circulation device 50 includes a first circulation passage 51 having an end of the circulation device 50 connected to the lower side of the tub 11, and the other end connected to the exhaust valve 42, a second circulation passage 52 having an end connected to the exhaust valve 42 and the other end connected to the upper side of the tub 11, and a circulation pump 53 installed in the second circulation passage 52.

The exhaust valve 42 which is connected to the exhaust pipe 41, the first circulation passage 51, and the second circulation passage 52 is implemented by a three-way valve capable of switching passages. When the first circulation passage 51 is communicated with the exhaust pipe 41 by the exhaust valve 42, the water is exhaust from the tub 11. When the circulation pump 52 is driven into the state wherein the first circulation passage 51 is communicated with the second circulation passage 52 by the exhaust valve 42, the water collected in the lower side of the tub 11 is circulated along the circulation passages 51 and 52 and is ejected through the ejecting nozzle 54 in the upper side of the tub 11.

Moreover, the washing machine employing the control method of the present invention includes an electrode device 60 having an electrode device case 61, a pair of electrodes (a first electrode 62 and a second electrode 63) installed in the electrode device case 61, and an electrode device power supply 64 (See FIG. 3) to supply a DC voltage to the pair of electrodes 62 and 63. The electrode device 60 serves as a sensor to measure turbidity of detergent water (water+detergent) or the rinsing water during the washing cycle or the rinsing cycle, and may be utilized to pasteurize the laundry, the tub 11, or the rotation drum 12 during the washing cycle or the rinsing cycle.

The pair of electrodes 62 and 63 of the electrode device 60 is installed on the circulation passage 52. In a case in which the electrodes 62 and 63 are installed on the circulation passage 52, since the electrodes 62 and 63 are submerged into the water only when the water circulates through the circulation passage 52, the electrodes 62 and 63 can be prevented from being contaminated, by submerging the electrodes 62 and 63 into the water for a long time. Moreover, when the electrodes 62 and 63 are installed on the circulation passage 52, the electrodes 62 and 63 measure the turbidity of the water so that the turbidity of the water can be more precisely measured (since the electrodes measure turbidity of only the water collected, surrounding the electrodes when the electrodes are installed in a specific position in the tub, the turbidity of the water cannot be precisely measured when the detergent is not dissolved uniformly in the water.)

The pair of electrodes 62 and 63 of the electrode device 60 are made of different materials. For example, the first electrode 62 may be a silver electrode containing silver (Ag) and the second electrode 63 may be a titanium electrode containing titanium (Ti). The second electrode 63 may be coated with platinum or iridium for the improvement of durability.

When the silver electrode is used as the first electrode 62, that is, as a positive electrode, a voltage is supplied to generate silver ions. Using a sterilizing power of the silver ions, the rotation drum 12, the tub 11, and the laundry in the rotation drum 12 can be sterilized.

Moreover, the use of the titanium electrode as the second electrode 63 is to prevent the electrodes 62 and 63 from being ionized and consumed when the electrode device 60 is used as a sensor during the washing cycle and the rinsing cycle. Titanium is minimally oxidized even when the voltage is supplied to the positive electrode, that is, the second titanium electrode, because of a low ionization.

Moreover, the washing machine employing the control method of the present invention, as illustrated in FIG. 3, includes a signal input unit 71, a lever detector 72, a current detector 73, and a controller 74.

The signal input unit 71 inputs operation information such as the washing course and addition of the rinsing selected by the user to the controller 74, and the level detector 72 detects the level of water supplied into the tub 11. The current detector 73 detects the magnitude of current flowing between the pair of electrodes 62 and 63 when the voltage is supplied to the pair of electrodes 62 and 63 and transmits the detected result to the controller 74.

The controller 74 is a microcomputer to control the washing machine based on the operation information inputted from the signal input unit 71, and stores washing time and the number of times of rinsing, which are predetermined according to a load (weight of laundry), in the selected washing course. The controller 74 also stores a current value Iw as a reference value that is used to determine whether excess detergent is added during the washing cycle, and a current value Ir as a reference value that is used to determine the turbidity of the rinsing water during the rinsing cycle. Since the detergent serves as electrolyte when being dissolved in water, the magnitude of the current detected when the electrodes 62 and 63 are submerged into the detergent water or the rinsing water is detected to find the quantity of the detergent dissolved in the detergent water or the rinsing water.

The controller 74 determines the quantity of the detergent added by the user or the quantity of the detergent remaining in the rinsing water during the rinsing cycle based on the information transmitted from the current detector 73, and changes conditions (for example, the number of times of the rinsing) for the rinsing cycle based on the determination. In other words, the controller 74 supplies a quantity of rinsing water that is greater than a predetermined quantity of rinsing water at the initial rinsing cycle to perform the rinsing cycle when the user adds an excessive quantity of the detergent. Moreover, when the magnitude of the current detected at the rinsing cycle is less than the reference value Ir, the controller 74 determines that the rinsing is sufficient, and finishes the rinsing cycle.

Hereinafter, the control method of the washing machine is configured as described above with reference to FIGS. 3, 4A and 4B. FIGS. 4A and 4B are flowcharts illustrating the control method of a washing machine according to the embodiment of the present invention.

When the laundry is put into the rotation drum 12, and the user selects the operation information such as the washing course, washing temperature, the number of times of rinsing, and the like, the operation information selected by the user is inputted to the controller 74 through the signal input unit 71.

Then, the controller 74 starts the washing based on the operation information inputted from the signal input unit 71, and first determines whether the operation is turned on (S100).

If the operation is turned on, the controller 74 detects the quantity of a load (weight of the laundry) put into the rotation drum 12 (S102) and sets the washing time a and the number of times of rinsing b based on the detected quantity of a load (S104).

Continuously, the controller 74 opens the water supply valve 31 to add the detergent into the tub 11 together with the water (specifically, the washing water) for the washing of the laundry (S106).

After the supply of the detergent water (the washing water+the detergent) into the tub 11, the controller 74 drives the circulation pump 53 of the circulation device 50 to circulate the detergent water through the circulation passages 51 and 52. Then, the detergent water located in the lower side of the tub 11 flows to the upper side of the tub 11 and is ejected into the rotation drum 12 through the ejecting nozzle 54, so that the laundry gets evenly wetted, and the detergent is uniformly dissolved in the water (S108).

The controller 74 determines whether a predetermined time has elapsed (S110), and supplies a voltage to the first and second electrodes 62 and 63 installed on the circulation passage 52 during the circulation of the detergent water when the predetermined time has elapsed. At that time, voltage is supplied to the positive electrode, that is, the second titanium electrode 63, and the negative electrode, that is, the first silver electrode 62. Then, the silver electrode, that is, the first electrode 62, can be prevented from being consumed due to oxidation. When voltage is supplied to the first and second electrodes 62 and 63, current flows through the detergent water passing through the circulation passage 52 while the current detector 73 detects the magnitude 11 of the current flowing between the two electrodes 62 and 63 (S112).

Then, the controller 74 determines whether the detected magnitude I1 of the current is equal to or greater than the reference value Iw (S14), and performs the washing cycle when the detected magnitude I1 is less than the reference value Iw (S120). In other words, the controller 74 performs the washing cycle in which the detergent water (water+detergent) is mixed with the laundry well due to the rotation of the rotation drum 12, and the washing is carried out by frictional force between the rotation drum 12 and the laundry and a force of falling laundry.

On the other hand, when the detected magnitude I1 of the current is equal to or greater than the reference value Iw as a result of the operation S114, the following operations are performed, and the washing cycle is performed. The controller 74 changes the number of times of rinsing is performed during the initial rinsing cycle and is to be performed later. In other words, the controller 74 sets the number of times of rinsing again such that the quantity of the rinsing water that is greater than the initially set quantity of rinsing water b can be supplied (S116). Moreover, when it is determined as described above, the controller 74 expects the washing time to be extended, adds a predetermined time (for example, time for performing the rinsing cycle once more) to the washing time a, and displays the added predetermined time on the display 14. The controller 74 displays a message that excess detergent has been added on the display 14 such that the user can reset the washing time on the display (S118).

When the washing cycle is finished, the rinsing cycle is started. When the initial rinsing cycle is started, the controller 74 opens the water supply valve 31 to supply as much as a predetermined quantity of rinsing water to the tub 11. Since it was determined that an excessive amount of detergent has been added at the above-mentioned washing cycle, the rinsing water, as much as the re-set quantity, is supplied when the quantity of the rinsing water is set again at the initial rinsing cycle. On the other hand, when it is determined that excess detergent has not been added, and the washing cycle is performed as it is, as much rinsing water as the initially set quantity of the rinsing water b is supplied (S122).

When the rinsing water is supplied, the initial rinsing cycle is performed, and the controller 74 counts that the rinsing cycle has been performed once (S122 and S124).

When the initial rinsing cycle is finished, the next rinsing cycle is performed, and the controller counts that the rinsing cycle has been performed once more. As such, by counting of the number n times of performing the rinsing cycles, every rinsing cycle prevents water and electric power from being wasted by restricting the number of the rinsing cycles to be performed. In the rinsing cycle after the initial rinsing cycle, rinsing water that constitutes as much as the initially set quantity b is supplied (S128 and S130).

Before the present rinsing cycle is finished, the controller 74 drives the circulation pump 53 to circulate the rinsing water in the tub 11 through the circulation passages 51 and 52, and supplies the voltage to the first and second electrodes 62 and 63. In this case, like the washing cycle, the voltage is supplied by regarding the titanium electrode, which is, the second electrode 63, as a positive electrode and the silver electrode, which is the first electrode 62, as a negative electrode. Then, the current flows through the rinsing water passing through the circulation passage 52, and the current detector 73 detects the magnitude I2 of the current flowing between the two electrodes 62 and 63 (S132).

Continuously, the controller 74 determines whether the detected magnitude I2 of the current is equal to or less than the reference value Ir (S134).

When it is determined that the detected magnitude I2 of the current is equal to or less than the reference value Ir, the controller 74 perceives the present rinsing cycle to correspond to a final rinsing cycle and changes polarities of the voltage to be supplied to the first and second electrodes 62 and 63 by controlling the electrode device power source 64 before the present rinsing cycle is finished (S138). In other words, the controller 74 supplies the voltage by regarding the silver electrode, that is, the first electrode 62, as a positive electrode and the titanium electrode, that is, the second electrode 63, as a negative electrode. Then, the oxidation is generated from the first electrode 62 and silver ions are supplied to the rinsing water. The silver ions are supplied into the rotation drum 12 together with the circulating rinsing water to sterilize the laundry. As such, when the polarities of the voltage supplied to the first and second electrodes 62 and 63 are changed, the electrodes can be washed. In other words, when the voltage is supplied by regarding the first electrode 62 as a negative electrode and the second electrode 63 as a positive electrode, positively charged contaminants are attached to the first electrode 62 and negatively charged contaminants are attached to the second electrode 63. If the polarities of the voltage supplied to the two electrodes 62 and 63 are changed, the contaminants are removed due to repulsive force.

Meanwhile, when the detected magnitude I2 of the current exceeds the reference value Ir as a result of the determination at operation S134, it is determined whether the counted number n of the rinsings reaches a maximum permissible number N of times of rinsing (S136). As a result of the comparison, when it is determined that the counted number n of times of rinsing does not reach the maximum number N of times of rinsing, the operation S128 is performed once more so that the rinsing cycle is performed once more and the next operation is performed.

When it is determined that the counted number n of times of rinsing has reached the maximum number N of times of rinsing as a result of the comparison, the above-mentioned operation S138 is performed so that the laundry is sterilized and the contaminants are removed from the electrodes.

The controller 74 determines whether the rinsing time of the final rinsing cycle has elapsed (S140), finally finishes the rinsing cycle when the rinsing time has elapsed (S142), and finishes the washing operation after performing the dehydrating cycle (S144).

As described above, according to the present invention, the degree of contamination of the rinsing water is monitored such that the rinsing cycle is automatically finished at a time when the rinsing of the laundry is finished. Thus, the rinsing performance is reliably guaranteed, and the undesired waste of water and electric power can be prevented.

Moreover, according to the present invention, information that excess detergent has been added is noticed by the user when the user adds the quantity of the detergent more than a desired quantity so that the user can add a desired quantity of the detergent in the future.

Further, in the present invention, the number of times of the rinsing cycle is restricted so that the rinsing cycle can be prevented from being continuously repeated even when the electrode device malfunctions.

According to the present invention, turbidity measuring and sterilization of the rinsing water can be performed while simultaneously using the electrode device.

Moreover, according to the present invention, the contaminant attached to the electrodes is automatically removed so that a lifespan of the electrodes is elongated, and the operation reliability of the electrode device can be guaranteed.

Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents. 

1. A control method of a washing machine of measuring turbidity of rinsing water and determining whether a rinsing cycle is finished, comprising: circulating the rinsing water through a circulation passage; measuring a magnitude of current flowing through the rinsing water by supplying a voltage to electrodes installed in the circulation passage; and comparing the detected magnitude (I2) with a reference value (Ir) and determining whether the rinsing cycle is finished based on the comparison.
 2. The control method of the washing machine according to claim 1, wherein when the detected magnitude (I2) of the current is equal to or less than the reference value (Ir), the rinsing cycle is finished, and when the detected magnitude (I2) of the current is greater than the reference value (Ir), another rinsing cycle is added and performed.
 3. The control method of the washing machine according to claim 1, further comprising: circulating detergent water through the circulation passage during a washing cycle performed prior to the rinsing cycle; detecting a magnitude (I1) of current flowing in the detergent water when a voltage is supplied to the electrodes; and determining whether a quantity of detergent added by a user is excessive by comparing the detected magnitude (I1) with a reference value (Iw).
 4. The control method of the washing machine according to claim 3, wherein when the detected magnitude (I1) is equal to or greater than the reference value (Iw), information that excess detergent has been added is displayed on a display.
 5. The control method of the washing machine according to claim 3, wherein when the detected magnitude (I1) is equal to or greater than the reference value (Iw), and a number of rinsing cycle times is added, and an elongated washing time is displayed on a display.
 6. The control method of the washing machine according to claim 3, wherein when the detected magnitude (I1) is equal to or greater than the reference value (Iw), a quantity of the rinsing water to be supplied at an initial rinsing cycle is re-set.
 7. The control method of the washing machine according to claim 1, wherein the electrodes are made of different materials, and the control method further comprises changing polarities of the voltage supplied to the electrodes for a predetermined time before the rinsing cycle is finished.
 8. The control method of the washing machine according to claim 1, wherein one electrode comprises a silver electrode containing silver and another electrode comprises a titanium electrode containing titanium, and the titanium electrode is regarded as a positive electrode when the voltage is supplied to the electrodes.
 9. The control method of the washing machine according to claim 1, further comprising: counting a number of rinsing cycle times; and finishing rinsing based on comparing the counted number of rinsing cycle times with a maximum number of rinsing cycle times.
 10. A control method of a washing machine comprising: circulating detergent water collected in a tub through a circulation passage during a washing cycle; supplying a voltage to a pair of electrodes made of different materials and installed in the circulation passage to determine whether a quantity of detergent contained in the detergent water is excessive; circulating rinsing water collected in the tub through the circulation passage during a rinsing cycle; detecting a magnitude (I2) of a current flowing through the rinsing water by supplying the voltage to the pair of electrodes; and comparing the detected magnitude (I2) of the current with a reference value (Ir) and finishing the rinsing cycle when the detected magnitude (I2) is equal to or less than the reference value (Ir).
 11. The control method of the washing machine according to claim 10, further comprising: counting a number of rinsing cycle times; and finishing the rinsing cycle even when the detected magnitude (I2) exceeds the reference value (Ir) when the counted number of rinsing cycle times reaches a maximum number of rinsing cycle times.
 12. The control method of the washing machine according to claim 10, wherein one of the pair of electrodes comprises a silver electrode containing silver and the other electrode comprises a titanium electrode containing titanium.
 13. The control method of the washing machine according to claim 12, wherein the titanium electrode is a positive electrode when the voltage is supplied to the pair of electrodes.
 14. The control method of the washing machine according to claim 12, wherein the voltage is supplied while using the silver electrode as a positive electrode for a predetermined time before the rinsing cycle is finished.
 15. The control method of the washing machine according to claim 10, wherein when it is determined that an excessive quantity of the detergent is contained in the detergent water, information that the excessive quantity of the detergent is contained in the detergent water is displayed on a display, and a quantity of the rinsing water to be supplied at an initial rinsing cycle is re-set.
 16. A control method of a washing machine comprising: circulating detergent water collected in a tub through a circulation passage during a washing cycle; and supplying a voltage to a pair of electrodes made of different materials and installed in the circulation passage to determine whether a quantity of detergent contained in the detergent water is excessive.
 17. The control method of the washing machine according to claim 16, wherein the determining whether a quantity of detergent contained in the detergent water is excessive comprises: detecting a magnitude (I1) of a current flowing through the detergent water by supplying the voltage to the pair of electrodes; and determining whether a quantity of detergent added by a user is excessive by comparing the detected magnitude (I1) with a reference value (Iw). 